Light-emitting diodes (referred to hereinafter as LEDs) represent one of the most popular light-emitting devices today. Due to the small form factor and low power consumption, LEDs are widely used in electronic mobile devices as indicator lights, light sources for Liquid Crystal Displays or LCDs, as well as flashes in camera phones, digital cameras and video recording devices. Compared to Xenon flashes used in most cameras, LEDs are superior in terms of size and power consumption. For example, an LED in a flash application may have a thickness of 0.6 mm compared to Xenon flashes that has a thickness of 1.3 mm. The small form factor makes LEDs suitable in mobile camera devices or mobile phones with a camera feature that may have an overall thickness less than 5 mm. In addition, unlike Xenon flashes, LEDs do not require charging time before use.
Generally, most light-emitting devices are not made for a single application, but for multiple applications. The light-emitting devices used in flashes are usually high power and high output light sources. Therefore, other suitable applications for light-emitting devices used in flashes are high power applications, such as indicator lights, light sources used in lighting fixtures or light sources used in infotainment displays. Electronic infotainment display systems are usually large-scale display systems, which may be found in stadiums, discotheques, electronic traffic sign displays and infotainment billboards along streets and roadways. Electronic infotainment displays may be configured to display text, graphics, images or videos containing information or entertainment contents.
Most of the flashes used today are white light sources. However, light produced by light source dies in most LEDs are generally a narrow banded light having a peak wavelength ranging from ultra violet to green wavelength. The output of the light source die is then typically converted to a broad spectrum white light by means of a wavelength-converting material. One example of a wavelength-converting material is phosphor. The wavelength-converting material may absorb a portion of light, resulting in light loss. The light lost is usually not substantial, but may be significant if the wavelength-converting material is thick.
There are several design considerations in designing a light-emitting device, such as viewing angle, color point, heat dissipation, power consumption and form factor, to name a few. Generally light-emitting devices are designed giving priority to design considerations in a primary application. For example, the light-emitting devices targeted for a flash application in camera devices tend to be small in form factor and have a high light output. However, light-emitting devices can often be used outside the targeted, primary application.